Here is an idea for you (if you have not tried it yet). I have found that grinding the welds down with a thin cutting disc on the angle grinder will prevent the metal from getting overheated. After I get the welds close to level, I finish them off with a flap disc. It may be worth a try to see if you like it better. Either way, you end up digging black stuff out of your nose and ears for the next few days!
